Ultrasonic calendering of paper webs

ABSTRACT

More rapid and improved calendering of a paper web is achieved by vibrating at ultrasonic frequency at least one of the calendering rolls at a nip through which the web runs. Accelerated attainment of gloss of the finished sheet through friction or shear stress, and smoothness of the finish sheet by pressure or compressive stress are provided for.

United States Patent 1 Busker ULTRASONIC CALENDERING OF PAPER WEBS [75] Inventor: Leroy l'l Busker, Rockton, I11.

[73] Assignee: Nakajima All Co., Ltd., Tokyo,

Japan 22 Filed: Sept. 17,1973

[21] Appl. No.: 397,887

[52] US. Cl. 100/35; 29/110; 68/3 SS;

[51] Int. Cl. B30B 13/00; B30B 3/04 [58] Field of Search 72/199, 35; 100/155, 172, 100/176; 156/73, 580, 582; 29/115, 110;

[56] References Cited UNITED, STATES PATENTS Jones 72/199 [4 1 Sept. 30, 1975 3,224,915 12/1965 Balamuth et a1 156/580 UX 3,550,419 12/1970 Fox et al...l 72/199 3,620,061 1 1/1971 Cunningham et al..

3,678,720 7/1972 Dickey et a1 72/199 X Primary Examiner-Peter Feldman Attorney, Agent, or Firm-Gifford, Chandler & Sheridan [5 7 ABSTRACT More rapid and improved c'alendering of a paper web is achieved by vibrating at ultrasonic frequency at least one of the calendering rolls at a nipthrough which the web runs. Accelerated attainment of gloss of the finished sheet through friction or shear stress, and smoothness of .the finish sheet by pressure or compressive stress are provided for.

8 Claims, 5 Drawing Figures US. Patent Sept. 30,1975 3,908,808

Fig. 5

This invention relates to calendering of paper webs and is more particularly concerned with accelerating the calendering process with improved calendering results. I f I Fundamental considerations of calendering of paper webs lead to the view that both Compressive andshear stress must be app'liedsimultaneously to accomplish the desired changes in surface andstructure. Evaluations are based on measurements. of printability, smoothness, caliper, o'pacityfiand' other measurements. Various prior studies have shown that pure hydrostatic pressure has little or no transforming effect on paper. I-lowever,.whena high compression stress'is applied.simultaneously'with a shear stress, the paper is-tranformed into a translucent horn-like mass. Supercalendering is employed to produce. glassine.with; desirable translucency. In calendering, simultaneous application of hyrostatic pressure-and shearstress gQCCUl'S in running of theweb throughthe nipsof the calender-rolls which apply rolling friction or deformation, Surface.

Engineering, Apr. 22, 1968, page 10 6) ,that technique,

has not, so far as I am informed, been employed in ca]- endering of paper webs, and thespecial conditions. and requirements for ..handling and treating the, relatively soft felted fiber structure of such,webs

It is; accordingly, an important object of the present invention to improve the calendering of pap er, webs Another object of the invention is to provide anew and improved methodbf and means reducing the number of calendering nips through which the paper webs must pass to attain the desired properties in the paper.

A further object of the invention is to provide a new and improved method of and means for applying both friction or shear stress and pressure or compressive stress in the calendering of paper webs.

Still another object of the invention is to provide for ultrasonic calendering of paper webs.

Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

FIG. 1 is a schematic illustration of one means for ultrasonic calendering.

FIG. 2 is a schematic illustration of a modified means for ultrasonic calendering.

FIG. 3 is a schematic illustration of a calendering roll for attaining another mode of ultrasonic calendering.

FIG14 is an end elevational view of the roll in FIG. 3; and

FIG. 5 is a schematic illustration of means for attaining multiple modes of ultrasonic calendering effects.

As illustrated in FIG. 1, a pair of calendering rolls and 11 mounted in any preferred paper calendering machine stackare adjuste'cl relative' to one another to receive a paper web' I2'therebtween and apply 'c'alendering'p ressure thereto as the paperru'n s'through the nip of the rolls, effecting compressionof the web. Ordinarily, the paper web is run through a plurality of indivi'dual' nips, the number depending upon the ultimate condition of smoothness and density desired in the paper.

nips through which the paper web 12 must run to attain the desired results is greatly reduced'. :This is achieved according ,to one p'referred mode by ,vibrating at ul trasonic frequency at least one of the rolls 10 and'l l 'i asf the web runs through the nip of the cooperatively rotate ing rolls. By way of example, the calender roll 11 comprisesahollow cylinder within which vibration effecting rneans are mounted inthe form of tightly fitted cylinders of an electrostrictive material 13 such as barium andcontract at the high frequency and with a'preferred amplitude, for example 0.7 mils". Inasmuch as smooth ness and other properties desired in the paper web 12 are-obtained indirect-proportion to the number of nips through ,which the web runs in a conventional calender, the number of cycles to which the web {is subjected to compressive stressin running through the single of i the rolls 10 and 11 should obtain-substantially thesirne results in this single pass as would be effectedj in r u'nning through the'same number'of individual a conventional'calender. For example, bys ubjecting web 12 to seven or eight cycles in the nip betweenith'e rolls 10 and-11 should achieve the same results running the web throughseveii oreightindividual nipsat the same speed and under the same conditions of paper web'qu'ality, moisture content, etc.

Not only compressive stress, but shear stress can be I applied and controlled in calendering the paper web. Friction or shear stress affects the surface or gloss characteristics of the finished sheet, whereas smoothness is produced more by pressure or compressive stress exerted on the paper web during calendering. For example, in FIG. 2 an arrangement is shown for implementing application of shear stress to a paper web 15 running through the nip of cooperatively rotating calender rolls 17 and 18, at least one of which is equipped to vibrate with ultrasonic frequency in a peripheral direction. In other words, the rotation of one of the rolls, in this instance the roll 18 is modulated ultrasonically to control the shear stress effect on the web 15. Means for attaining this end, comprise construction of the roll 18 as a hollow cylindrical shell having diametrically opposite longitudinally extending radial internal fins 19 respectively in face-to-face opposition to corresponding radial outwardly extending fins 20 on an axial support core 21, with electrostrictive material 22 secured to and between the pairs of fins 19, 20. High frequency electrical energy applied to the material 22 causes cooperative vibration of the fins l9 and 20 and thereby ultrasonic frequency modulation of normal rotation of the roll 18 as indicated by the double prong arrow, whereby to subject the web 15 to shear stress multiplied by the ultrasonic oscillatory vibrations of the pe- Accordi ng to the present in'vention'ithe number of riphery of the roll 18 in contact with the web running through the nip of the rolls 17 and 18.

Cross-machine shear-.stress may be applied to the paper web by having at least one of a pair of calender rolls vibrate at ultrahigh frequency longitudinally. For this purpose, at least one of the rolls of a pair of calender rolls may be constructed as exemplified in FIGS. 3 and 4, wherein a roll having at its opposite ends journals 27 rotatably supporting the roll in bearings 28 has means for effecting longitudinal high frequency vibrations of the roll as indicated by the double pronged arrow in FIG. 3. For this purpose, the roll may be equipped with a respective doughnut or ring 29 of electrostrictive material adjacent to each opposite end, as for example mounted in a groove 30 in each instance. These rings 29 are excited in alternating phase by high frequency electrical energy supplied by' a suitable source through leads 31. Thereby the roll is vibrated longitudinally at ultrasonic frequency while rotating in contact with a paper web running through the nip of a pair of calender rolls of which the roll 25 comprises one of the pair.

FlCuS represents the application of combined'modes of shear and compressive stress application to a paper web as it runs through the nip of a pair of calender rolls 37' and 38. In this instance shear stress is applied by the roll 37 vibrated at ultrasonic frequency oscilatably while rotating cooperatively with the roll 38 which is vibrated radially at ultrasonic frequency. For this purpose, the roll 37 may be vibrated in the manner of the roll.18 in FIG. 2, and the roll 38 vibrated in the manner of the roll 11 in FIG. 1. If preferred, longitudinal or reciprocal vibration may be applied to either of,

quency vibration of the rolls may be produced by other means for generating the vibrations than the electromechanical means described. For example advantage may be taken of natural frequencies of mass elastic systems. lt will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.

I claim as my invention:

1. A method of calendering paper web, comprising:

running the paper web through the nip of a pair of cooperatively rotating calender rolls;

and vibrating peripherally at ultrasonic frequency at least one of said rolls as the web runs through said nip.

2. A method according to claim 1, comprising ultrasonically vibrating both of said rolls in different modes of vibration.

3. A method according to claim 1, comprising vibrating said one roll radially and peripherally vibrating the other roll at ultrasonic frequency.

4. A method according to claim 1, comprising vibrating said one roll radially and vibrating the other of said rolls at ultrasonic frequency longitudinally.

5. Apparatus for calendering paper web, comprising:

a pair of cooperatively rotatable calendering rolls providing a nip through which the paper web runs;

'and means for vibrating peripherally at ultrasonic frequency at least one of said rolls as the web runs through said nip.

6. Apparatus according to claim 5, comprising means for ultrasonically vibrating both of said rolls in different modes of vibration.

7. Apparatus according to claim 5, comprising means for vibrating said one roll radially and means for peripherally vibrating the other roll at ultrasonic frequency.

8. Apparatus according to claim 5, comprising means for vibrating said one roll radially and means for longitudinally vibrating the other of said rolls at ultrasonic UNITED STATES PATENT ND TRADEMARK OFFICE QETIFICATE 0F CORRECTION 9 PATENT NO. 3, 908, 808

DATED September 30, 1975 INVENTOMS) I Leroy H. Busker it is certifi ed that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First Sheet of Patent change "Assignee: Nakajima All C0,, Ltd., Tokyo, Japan" t .m

Q N A ssignee: Beloit Corporation,

Beloit, Wisconsin-- ,Zvigncd and Salad this Q thirteenth Day Of April 1976 [SEAL] Arrest:

6 RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissimwr uj'lurer'rrs and Trademarks 

1. A method of calendering paper web, comprising: running the paper web through the nip of a pair of cooperatively rotating calender rolls; and vibrating peripherally at ultrasonic frequency at least one of said rolls as the web runs through said nip.
 2. A method according to claim 1, comprising ultrasonically vibrating both of said rolls in different modes of vibration.
 3. A method according to claim 1, comprising vibrating said one roll radially and peripherally vibrating the other roll at ultrasonic frequency.
 4. A method according to claim 1, comprising vibrating said one roll radially and vibrating the other of said rolls at ultrasonic frequency longitudinally.
 5. Apparatus for calendering paper web, comprising: a pair of cooperatively rotatable calendering rolls providing a nip through which the paper web runs; and means for vibrating peripherally at ultrasonic frequency at least one of said rolls as the web runs through said nip.
 6. Apparatus according to claim 5, comprising means for ultrasonically vibrating both of said rolls in different modes of vibration.
 7. Apparatus according to claim 5, comprising means for vibrating said one roll radially and means for peripherally vibrating the other roll at ultrasonic frequency.
 8. Apparatus according to claim 5, comprising means for vibrating said one roll radially and means for longitudinally vibrating the other of said rolls at ultrasonic frequency. 